European Published Patent Application No. 0 339 380 describes a device for coaxially connecting two parts in a rotatably fixed manner, where a transverse, threaded pin is used for axial fixing. However, such a device may be expensive to manufacture, since the transverse, threaded pin represents an additional part and a corresponding tap hole suitable for this transverse, threaded pin must be prepared.
A press-fit assembly for a rotor shaft is described in German Published Patent Application No. 37 32 223. In this context, the toothed region of a shaft is inserted into a bore of a receiving part, shavings being formed in response to the shaft being pressed in in a form-locked manner. Annular grooves are provided for collecting the shavings formed in response to the form-locked pressing. In addition, the shaft has at least two fitting regions (FIGS. 4, 6, 7). Therefore, the manufacturing of the press-fit structure is complicated and expensive due to, in particular, the at least two fitting regions and the annular grooves. Furthermore, it may be disadvantageous that a press fit for absorbing the axial forces is not present. Axial forces even allow rotor core 8 to strike rear walls and increase frictional losses.
A pinion fixture for planetary gears is described in German Published Patent Application No. 41 34 552, where a pinion is provided with a fitting region and a standardized, hardened, and ground, knurl toothing and is pressed into the receiving part at an elevated temperature. Annular grooves are provided for collecting the shavings. The fitting region and the toothing have different outer diameters. The manufacturing of this pinion fixture is also complicated and expensive, in particular, because of the annular grooves and the different outer diameters of the toothing and the fitting region. In this instance, it may also be disadvantageous that no reassembly of an already previously assembled pinion fixture is possible, for it is clearly mentioned in column 3, line 12 of German Published Patent Application No. 41 34 552, that a press fit is provided. When attaching the shaft for reassembly, this press fit, in particular in region 5, and the fact that the axial length of region 5 is greater than the axial length of region 3, do not allow the engagement of the gear teeth of the shaft with the inner gear teeth already pressed in and present in the bore from the first assembly, to be felt or sensed.
European Published Patent Application No. 0 784 758 describes a shaft fixture, which has two fitting regions (FIGS. 1 and 2, regions A and C). Upon inserting the shaft into the bore of a receiving part, the keyed connection is achieved by pressing it in in a form-locked manner. The torque is transmitted by toothed, knurled or milled region B. It may be disadvantageous that region C cannot transmit a torque. In this context, relative movements in regions A and C result in frictional fatigue fractures. It may also be disadvantageous that two fitting regions (regions A and C) are necessary, and that a large overall length is consequently necessary. In addition, the manufacture of two fitting regions is very expensive. Furthermore, the bore has three different diameters, which are also difficult to fabricate. Necessary regions A and C are exclusively centering aids, which do not contribute anything to the transmission of torque.
European Published Patent Application No. 0 661 474 describes a shaft fixture, which has two fitting regions and a bore having three different diameters. Such a shaft fixture is also expensive to manufacture. In another variant, a shaft fixture having only two different bore diameters is also described. This variant is also expensive, since the fitting regions and the inner walls of the bore must be machined so accurately, that, on one hand, no shavings are formed when introducing the shaft for pressing it into the bore, and that, on the other hand, after insertion, i.e., in the pressed-in state after assembly, no gaps are formed between the shaft and the inner wall of the bore. The torque is transmitted by toothed or milled region B. It may also be disadvantageous that region A cannot transmit a torque. Necessary regions A and C are exclusively centering aids for the pressing operation, which do not contribute anything to the transmission of torque. Reassembly is not possible or very difficult to carry out, since region C is longer than region B′ of the receiving part.
Described in European Published Patent Application No. 1 281 884 is a series of shafts 1, which are connectable to a receiving part that possesses a bore 3 having a single bore diameter. At least cylindrical region B2 and knurled region B1 of the shaft are pressed into this bore 3. In this context, it may be disadvantageous that reassembly is only possible with great difficulty, for after shaft 1 is pressed into the receiving part and then extracted again, it is impossible to find the gear-tooth position upon reattaching the shaft for the purpose of reconnection, since in the case of a slightly attached shaft, the milled edge in region B1 is outside of the receiving part and cylindrical region B2 must be pressed in by force. However, if cylindrical region B2 is reinserted deeply or far into the receiving part, it is only possible to rotate shaft 1 using a large force. Thus, when the milled edge of region B1 lightly meets the knurled inner edge of the receiving part produced by the original joining procedure and then rotation occurs, it is extremely difficult to sense the engagement of the milled edge with the knurled inner edge, for the torques required for the rotation necessary for this are large and the torque fluctuations produced by the engagement of the milled edge are very small. Thus, reassembly in a conventional manner, in particular, finding the engagement by hand, is impossible.